import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入需要购买的钢管长度（单位：米）：");
        double length = scanner.nextDouble();
        int numOfTubes = (int) Math.ceil(length / 3);
        System.out.println("需要购买 " + numOfTubes + " 根钢管。");
    }
}